1. Field of the Invention
The present invention relates to a liquid heating apparatus such as a fryer, a noodle boiling machine or the like, and in particular, to a liquid heating apparatus which can effectively heat a liquid in a liquid bath.
2. Description of the Related Art
Conventionally, a fryer used as this type of liquid heating apparatus has been disclosed in Unexamined Utility Model Publication (Kokai) No. 61-52152, for example. As shown in FIG. 9 and FIG. 10, the fryer 1 has a liquid bath 3 which is located on an upper portion of a main body 2, and a plurality of exhaust pipes 4 (four in FIG. 9) are arranged in a horizontal state at the substantially central position in a height direction of the liquid bath 3. These exhaust pipes extend penetratingly from one end side 3a (front side of the main body 2) toward the other side 3b (rear side of the main body 2). Each exhaust pipe 4 is provided with connective pipes 5a and 5b which are inclined right and left and alternately extend in a shape of cross in the exhaust pipe 4, at a predetermined interval in a longitudinal direction thereof.
Moreover, a lower portion on one end side 3a of the liquid bath 3 is formed with a combustion chamber 9 which comprises a horizontal wall 6, a vertical wall 7 and a cover 8 downwardly extending from the front end of the horizontal wall 6, and a gas burner 10 is arranged in the combustion chamber 9. A bottom portion of the liquid bath 3 on the lower portion of the exhaust pipe 4, is inclined so as to become low on its forward side, and a portion just under the bottom portion is provided with a drain cock 11, and further, a waste oil box 12 is arranged at a downward position of the drain cock 11 in the man body 2.
In the fryer 1, when the combustion chamber 9 is filled with a combustion gas generated by a combustion of the gas burner 10, the horizontal wall 6 of the liquid bath 3 is directly heated so as to heat an oil 13 in the liquid bath 3. Then, the combustion gas comes into the exhaust pipe 4, and flows through the interior of exhaust pipe 4 as shown by an arrow A, and thus, is discharged from a discharge cylinder 14 to the outside.
In this case, four exhaust pipes 4 are arranged in a horizontal state; therefore, the oil 13 in the liquid bath 3 is heated by the combustion gas flowing through the exhaust pipe 4 while being heated by the connective pipes 5a and 5b located in the exhaust pipe 4. Whereby an upper portion of the liquid bath 3 from the exhaust pipe 4 becomes a high temperature section; on the other hand, a lower portion of the liquid bath 3 from the exhaust pipe 4 becomes a low temperature section. Further, a food is deep-fried in the oil 13 of the high temperature section while being prevented from falling into the low temperature section by a net 15 arranged on the upper portion of the exhaust pipe 4.
However, this fryer 1 has a construction in which four cylindrical exhaust pipes 4 are arranged at the lower portion of the liquid bath 3, and the exhaust pipe 4 is provided with the totaled six connective pipes 5a and 5b arranged like a shape of cross. For this reason, a heating surface area of the combustion gas flowing through the exhaust pipe 4 is small with respect to the exhaust pipe 4; as a result, it is impossible to effectively the oil 13 of the liquid bath 3 by means of the gas burner 10. Thus, the aforesaid fryer 1 has a problem that it is difficult to obtain a sufficient heat efficiency.
Moreover, a temperature of the combustion gas flowing through the exhaust pipe 4 becomes highest at an inlet side on the combustion chamber 9 side of the exhaust pipe 4, and becomes lowest at an outlet side on the discharge cylinder 14 side. In the above fryer 1, the totaled six connective pipes 5a and 5b are merely extended in a diametrical direction of the exhaust pipe 4, and are arranged along the longitudinal direction thereof at a substantially constant interval. For this reason, it is difficult to obtain a heat conduction along a temperature gradient of the combustion gas flowing through the exhaust pipe 4; as a result, there is a problem that a temperature difference is easy to be generate in the oil 13 in the longitudinal direction of the liquid bath 3. In addition, a pressure loss is easy to be generated in an exhaust pipe 4 section forming a heat exchange section, and an outer dimension of the exhaust pipe section becomes large; for this reason, there is a problem that a cleaning performance is worse.